EP1672225B1 - Valve arrangement and method of controlling a double-acting hydraulic consumer - Google Patents

Abstract

The arrangement has a direction control valve (14) forming a metering orifice. The control valve is attached to an individual pressure scale (12) for keeping the pressure constant over the orifice. The scale is switched into a locking position in a predetermined operating condition of the load. A pilot valve (13) subjects a control surface of a control piston with the pressure from a pressurizing medium source for switching the scale. An independent claim is also included for a method for controlling a double acting consumer, in particular, a hoisting gear of a mobile implement.

Description

The invention relates to a valve arrangement and a method for controlling a double-acting consumer according to the preamble of patent claim 1 and of independent patent claim 8.

Such valve assemblies are used, for example, to control the work functions of mobile implements, such as tractors or excavators. The control of these hydraulic functions is usually via a very compact control block, in which all the essential directional and control valves are combined into one unit. Such a control block is described for example in the catalog 1 987 760 507 (electronic hydraulic hitch control for tractors) of the applicant. Further details can be found in the post-published application with the official file number 10 2004 033 315.7 or in the US 51 86 000 ,

Modern tractors are designed for example with a Heckhubwerk and a front lifting, the lifting cylinder can be acted upon by the control pressure with pressure medium, which is funded by a pump which is controlled so that in a pump line to a certain pressure difference across the load pressure of the consumer lying pump pressure prevails. Both the rear and the front lift are designed to double acting in modern tractors, each of the consumers are associated with electro-hydraulically actuated directional valves, which are controlled by an electric control unit of the mobile vehicle. The setpoints are for example via a front panel or a rear panel set inside the cabin. In certain operating conditions, the usually double-acting consumers can also be operated in single-acting mode, in which case, for example, a pressure chamber of the consumer is relieved at very low pressure to the tank, so that the consumer behaves like a single-acting consumer and, for example, lifting the hoist by supplying the Pressure medium to the other pressure chamber takes place while the lowering takes place solely by the weight of the load, the first-mentioned pressure chamber is relieved. In tractors usually a rear push button or a front button is provided, which are arranged on the rear or front of the tractor and make it possible to operate the hoists from the outside - for example, for coupling a working device. With simultaneous control of several consumers, it may happen that a greater pressure medium requirement than the maximum adjustable flow rate of the pump is present - the system gets into saturation, it can lead to a shortage of consumers, with some downstream consumers remain stationary. This can be critical in certain applications.

In contrast, the invention has for its object to provide a valve assembly and a method for driving a double-acting consumer, in which the risk of undersupply is reduced.

This object is achieved with regard to the valve arrangement by the features of patent claim 1 and with regard to the method by the features of claim 8.

According to the invention, the valve arrangement for controlling a double-acting consumer has a variable one Metering orifice, which is associated with an individual pressure compensator, via which the pressure drop across the metering orifice can be kept constant independent of the load pressure. According to the invention, this individual pressure compensator can be brought into a blocking position under certain operating conditions, for example when lowering a load, so that despite the controlled metering orifice of the pressure fluid flow path is shut off from a pressure medium source to the pressurized medium pressure chamber of the consumer. That is, according to the invention can be shut off depending on the operating condition of the pressure medium flow to the consumer, so that the system does not reach the saturation and the risk of undersupply of consumers is reduced.

In a particularly preferred embodiment, the individual pressure compensator is associated with a pilot valve via which an effective in the closing direction control surface of a control piston of the individual pressure compensator with the pressure of a pressure medium source of the system, usually a LS pump is acted upon, so that the control piston regardless of the on him acting load pressure can be brought into its blocking position. Since the pilot valve only has to pass relatively small control oil volume flows, it can be designed to be relatively small - with this small pilot valve, however, a comparatively large pressure medium volume flow can be switched on or off. The solution according to the invention works particularly advantageous, for example, when the consumer is operated in a single action and - for example, when lowering the consumer - the increasing pressure chamber is separated by the inventive valve assembly and the inventive method of the pressure medium supply. It is then consciously taking the form of a negative pressure in this increasing pressure chamber and a resulting foaming and outgassing in air - however, these effects can occur even with conventional control of Hubwerkszylindern, also cause the foaming and the air outgassing no failure of the system and can therefore be accepted.

The pilot valve is preferably designed as an electrically actuated 2-way switching valve that shuts off a connection between the pressure chamber of the individual pressure compensator and a pump line in its spring-biased basic position and opens this connection in its switching position.

In order to avoid in this switching position, a flow of control oil through the control line usually present, a nozzle is arranged in this.

This nozzle can be dispensed with if the pilot valve is designed as a 3/2-way switching valve, which shuts off a connection between the pressure chamber and the pump line in its spring-biased basic position and the aforementioned control line aufsteuert and shuts off in its switching position, this control line and the pressure chamber of the individual pressure compensator subjected to the pressure in the pump line.

The invention with depending on the operating state in a locking position can be brought individual pressure balance can be used both in LUDV systems as well as upstream or downstream LS individual pressure compensator. In the DE 198 31 595 A1 the applicant is a LUDV system disclosed in which a LUDV individual pressure compensator is moved when a predetermined load pressure is exceeded in a blocking position, this maximum load pressure is selected so that the associated consumer can be supplied with a sufficient amount of pressure medium. The invention operates according to a completely different concept, according to which the pressure medium supply to a consumer depending on the operating state is completely shut off - this shut-off is independent of the load applied to the load.

In the case in which a Hubwerksventilanordnung is driven by the method according to the invention, those operating conditions in which the individual pressure compensator is brought into its blocking position, for example, be present when a refilling of a pressure chamber is not required.

Other advantageous developments of the invention are the subject of further subclaims.

• Fig. 1 einen Hydraulkschaltplan eines Heckhubwerks eines Traktors;
• Fig. 2 eine Detaildarstellung einer Hubwerksventilanordnung aus Fig. 1 und
• Fig. 3 ein weiteres Ausführungsbeispiel einer Hubwerksventilanordnung für einen Traktor.

In the following preferred embodiments of the invention will be explained in more detail with reference to schematic drawings. Show it:

• Fig. 1 a hydraulic circuit diagram of a rear lift of a tractor;
• Fig. 2 a detailed view of a Hubwerksventilanordnung Fig. 1 and
• Fig. 3 Another embodiment of a Hubwerksventilanordnung for a tractor.

The invention will be explained below with reference to a hoist arrangement of a tractor. In principle, however, the circuit according to the invention can also be used with other double-acting consumers of a mobile working device.

Modern tractors are designed with at least one hoist 2, which has a double-acting lifting cylinder 6, the pressure chambers can be acted upon via a Hubwerksventilanordnung 8 invention with pressure medium or connected to a tank, which is composed with the directional valves for controlling the other consumers of the tractor to a control block ,

A Heckhubwerk 2 according to Fig. 1 can be used in different operating states. In the work area "carry" the Heckhubwerk and, where appropriate, the attached implement is either lifted off the ground or it is worn in contact with the ground with a predetermined support force. This work area occurs, for example, when plowing or when cultivating. In the working area "pressing" the Heckhubwerk 2 is driven so that a force acting in the direction of the ground pressure force is applied. Such a setting is, for example, move in active plow or required by a packer. In a load-free intermediate position in which the Heckhubwerk 2 is not acted upon by a force, this is due to its own weight on the ground. Such a load-free intermediate position is - as described below - adjusted by adjusting the Hubwerksventilanordnung 4 in a floating position.

The Hubwerksventilanordnung executed in disc design 4 has a pressure port P, a tank port T, a LS port LS and two working ports A, B. The pressure port P is connected via a pump line with a variable displacement pump 8, the discharge pressure in response to the highest, to the Consumers of the tractor is applied load pressure. This load pressure is tapped at the LS port. An LS control in which the flow rate of the pump depending is set by the highest load pressure, but is not a prerequisite for the system according to the invention.

The pressure port P is connected via an inlet channel 10 to an input port P 'of an individual pressure compensator 12 whose output port A' is connected to an input port P "of a continuously variable directional control valve 14. Its return port R is connected via a return passage 16 to the tank port T of the Hubwerksventilanordnung 4. The directional control valve 14 has two working ports A "and B" (see Fig. 2 ), which are connected via working channels 18, 20 with the two working ports A, B of the Hubwerksventilanordnung 4. The individual pressure compensator 12 is associated with a pilot valve 13, via which the individual pressure compensator 12 can be switched over into its blocking position under certain operating conditions.

In each working channel 18, 20 is a respective sink module 22, 24 is provided, which serves in a basic position as a pilot-operated check valve for leak oil-free clamping of the lifting cylinder 6 of the Heckhubwerks 2 and controls in a control position flowing back from the lifting cylinder 6 pressure medium flow in the sense of a flow control.

The working channel 20 can be connected to the tank connection T downstream of the sink module 24 via a pilot-controlled, proportionally adjustable pressure-limiting valve 26. The pressure in the other working channel 18 is limited by a secondary pressure relief valve 28. The lifting cylinder 6 is - as mentioned - designed double-acting, with an effective in the direction of "lowering" annular space 30 with the working port B and in the direction of "lifting" effective pressure chamber 32 is connected to the working port A of Hubwerksventilanordnung 4. About the lifting cylinder 6, a pivotally mounted on a lifting shaft 34 arm 36 and other coupling elements are actuated, where, for example, an attachment, such as a seed drill or a plow 38 is grown.

Details of the Hubwerksventilanordnung 4 are based on the enlarged view in FIG. 2 explained.

A pressure compensator piston of the pressure compensator 12 is acted upon by a pressure compensator spring 40 and by the pressure tapped in the opening direction via a channel 42 from a load-signaling duct 44 connected to the LS connection and by the pressure in a control duct 46 in the closing direction, which is between the pressure compensator 12 and the pressure compensator Directional valve 14 branches off from the inlet channel 10. From the control channel 46 branches off a pilot control line 70, which is guided to the output terminal of the pilot valve 13, whose input terminal is connected via a pilot pressure channel 72 to the upstream of the pressure compensator 12 located part of the inlet channel 10. The pilot valve 13 is biased via a pilot valve spring 74 in its illustrated blocking position in which the connection between the pilot pressure passage 72 and the pilot control line 70 is shut off. That is, in this basic position acts on the effective in the closing direction pressure chamber of the pressure compensator 12, the pressure which is tapped via the control channel 46 downstream of the pressure compensator 12. In this control channel 46, a nozzle 76 is provided which minimizes a flow of the control oil through the control channel 46 when switching the pilot valve 13 in its passage position. The switching of the pilot valve 13 via a switching magnet 78, wherein the on-board voltage is used for switching. As will be explained in more detail below, this switching takes place under certain operating conditions. In the switching position of the effective pressure in the closing direction pressure chamber of the pressure compensator 42 is applied to the pump pressure, so that the control piston moves into its closed position and the pressure medium flow is shut off to the consumer.

The LS channel 44 leads to a control connection LS '' of the directional control valve 14. This has two more control terminals X, whose output side control terminals XA and XB are assigned. The actuation of the directional control valve 14 via a pilot valve arrangement, which in the illustration FIG. 2 is formed by two electro-hydraulic pilot elements 45, 47. The triangle 49 indicates the control oil supply, for example a control oil pump, to these pilot control elements 47, 45. Via the pilot elements 47, 45, control oil can each be fed to a control chamber of the directional valve 14 until a valve slide 50 assumes a working position. This is recorded via a transducer. As soon as the desired position is reported by this, the pilot element 47, 45 is brought back into its neutral position. The position of the valve spool 50 is maintained regulated by the pilot elements 47, 45 are driven in accordance with the signal of the position transducer. These are connected via control lines 52 and 54 with the pilot oil supply 49. The valve spool 50 is biased via a Zentrierfederanordnung 56 in its illustrated basic position (0), in which the LS channel 44 is connected to the tank channel 16 and all other aforementioned connections are shut off.

The valve body of the two sink modules 22, 24 are each acted upon by a spring 58 and by the individual load pressure tapped at the outlet A '' or B '' via pressure compensator ducts 60, 62 downstream of the directional control valve 14 into its basic position (a) in which the Lowering modules 22, 24 act as check valves, which allow a flow of pressure medium to the terminals A, B. In Opening direction, the valve body of the sink modules 22, 24 respectively acted upon by the voltage applied to the terminal XA and XB control pressure, which is tapped via a Entsperrkanal 64, 66. This control pressure can correspond, for example, to the inlet pressure of the pilot control elements 45, 47.

The structure of the Hubwerksventilanordnung with the individual pressure compensator 12, the continuously adjustable directional control valve 14 and the two downstream sink modules 22, 24 substantially corresponds to the conventional solution of the valve SB23 LS, so that only the essential elements for understanding the invention are described in the following and in In this regard, reference is made to the existing state of the art for the directional control valve SB23 LS.

If, for example, the lifting cylinder 6 is to be moved to raise the plow 38, the valve spool 50 of the directional control valve 14 is displaced via the pilot control element 45 into one of its positions marked with (b). In this case, a metering orifice is opened, which is connected downstream of the individual pressure compensator 12. Depending on the orifice size, the pressure compensator 12 adjusts to a control position in which the pressure drop across the orifice plate is kept constant and thus a pressure-medium-independent pressure medium volume flow is set. This pressure medium volume flow is in the control positions indicated by (b) via the pressure compensator 12, the pressure port P '' and the output port A '' of the directional control valve 14 to the input port PDW of the sink module 22 and via its output port ADW to the working port A of the Hubwerksventilanordnung 4 and from there guided in the bottom-side pressure chamber 32 - the lifting cylinder 6 extends. The displaced from the annulus 30 pressure fluid flows through the working port B of the Hubwerksventilanordnung 4, the working channel 20, the output port BDW and the input terminal PDW of the sink module 24 to the terminal B '' of the directional control valve 14 and from there via the return port R, the tank channel 16 and the tank port T back to the tank. This return flow is made possible in that the control pressure applied to the pilot valve arrangement 49 is tapped via the control connection X and the output connection XB of the directional control valve 14 and applied via the unlocking channel 66 to the valve body in the opening direction, so that the sink module 24 unlocks and the return flow of the pressure medium to the tank T possible. In these (b) marked positions of the sink module 24, this acts as a discharge pressure balance over which the running pressure medium volume flow is regulated to some extent.

For pressing an implement supported by the hoist, the directional control valve 14 is displaced into one of its control positions marked with (a), so that the pressure medium is supplied via the sink module 24 in its return function to the annular space 30, while the pressure medium flowing out of the bottom pressure chamber 32 is discharged through the unlocked drain module 22 and the directional control valve 14 flows towards the tank. The unlocking takes place via the control pressure, which is guided via the control terminals X, XA of the directional control valve 14 and the Entsperrkanal 64 to the effective opening direction in the control surface of the sink module 22.

For load-free application, the directional control valve 14 is moved into its floating position (end position c), in which both lowering modules 22, 24 are unlocked and moved into their through position marked with (b) and the working connections A, B and the control connection LS are connected to the tank connection T. and the input terminal P "is shut off.

In the working range "pressing", the maximum pressure in the working channel 20 is limited to a value of, for example, between 0 to 250 bar by suitably setting the proportionally adjustable pressure-limiting valve 26. Via the secondary pressure limiting valve 28, the pressure in the working channel 18 (port A) is limited to a maximum pressure set below the pump pressure. The construction of such secondary pressure relief valves is known, so that further explanations are unnecessary. The construction of the pilot operated proportionally adjustable pressure relief valve 26 is known per se - a piston of the pressure relief valve 26 is loaded via a weak compression spring and by the pressure in the spring chamber against a valve seat in a closed position. The pressure in the spring chamber is limited by the force applied to a closing cone by means of a proportional magnet. The control of the proportional solenoid via the control unit 16.

Not shown are pressure sensors, via which the pressures in the working channels 28, 30, the pressure at the pressure port P, the load pressure and other pressures can be detected.

If, for example, the rear lifting mechanism is to be operated with single action, then the pressure limiting valve 26 is set to a minimum value, for example 5 to 8 bar, so that a minimum pressure is set at the working connection B and thus in the annular space 30 of the lifting cylinder 6. Now via the electrohydraulic hoist control (EHR) - as in the DE 10 2004 033 315.7 described - issued a lowering signal and activates a motion control, the directional control valve 14 is not lowered after lowering as in the double-acting function in its neutral position (0) but in the floating position (c) - the hoist can then adjust to any unevenness of the soil. The set behavior corresponds to that of conventional single-acting lifting gear valves.

If, for example, several other consumers are connected in addition to the rear linkage 2, an undersupply can be avoided according to the invention by the pilot valve 13 being switched to its passage position by energizing the switching magnet 78. As a result, the control piston of the pressure compensator 12 is brought into its closed position by the pump pressure picked off via the pilot pressure duct 72 and the pilot control line 70, so that the pressure medium connection to the enlarging annular space 30 is shut off. That is, it is no pressure medium in the increasing annular space 30 refilled and the Heckhubwerk 2 remains in contact with the ground simply stand and thus forms the previously known single-acting hoisting behavior almost completely. There remains a small control oil volume flow of P via the pilot pressure passage 72 and the pilot valve 13 (in open switching position), the pilot control line 70, the nozzle 76, the control channel 46, etc. for Hubwerkszylinder 6. This volume flow fills the cylinder chamber slowly, ie without significant influence of for other consumers required pressure medium volume flow. The pressure medium volume flow not required by the lifting cylinder 6 can be supplied to the further consumers, so that their undersupply can be avoided. The circuit according to the invention and the method according to the invention thus make it possible, on the one hand, to avoid a shortage of consumers and, on the other hand, a double-acting consumer can be controlled in such a way that it displays the behavior of single-acting consumers in a functionally identical manner. As mentioned above, the resulting disadvantage (foaming, air outgassing) in To be taken. The nozzle 76 minimizes the loss of control oil via the control channel 46, so that the pressure compensator 12 can be switched very quickly into its blocking position.

The pump pressure is sufficiently high in all operating conditions to close the individual pressure compensator 12 safely. Even in the case that there is already a shortage of supply prior to actuation of the pilot valve 13, ie, the pump pressure and the consumer pressure are almost the same, a pressure medium volume flow will set on the rear lift due to the low load (pulling consumer). This leads to a pressure drop across the directional valve slide control edge and thus to a sufficiently large pressure difference for closing the pressure compensator 12th

The switching on of the pump pressure according to the invention and the resulting shutting off of the pressure medium supply of a consumer can take place in all operating states in which a cylinder side does not necessarily have to be refilled. Such operating conditions occur when no pressure medium is needed on the sink side of the hoist cylinder and there is a risk that another consumer will stop due to undersupply. The switching on of the pump pressure according to the invention via the pilot valve 13 can thus take place during lowering of the hoist in its control function (that is not in the transport position in which a vibration damping takes place or when the lowering is controlled via a rear switch) and the above-described single-acting operation. The concept according to the invention is not applied even if a "cut" is active in the operating state "sinking", as it is known in the art DE 10 2004 033 315.7 is described. At this cut a force applied in the lowering direction is limited to a maximum value.

Fig. 3 shows an embodiment in which the nozzle 76 can be dispensed with. In this case, the pilot valve 13 is designed as a 3/2-way switching valve, wherein the pilot pressure channel 72 is connected to a first input terminal and the control channel 46 to a second input terminal. In its spring-biased home position, the pilot valve 13 connects according to Fig. 3 the control channel 46 with the pilot control line 70, which extends from the output terminal of the pilot valve 13 to the closing chamber in the effective pressure chamber of the pressure compensator 12. In the basic position of the pilot pressure passage 72 is shut off - thus acts on the pressure compensator 12 in the closing direction of the pressure in the area between the directional control valve 14 and the pressure compensator 12. If now the pressure medium supply to the consumer are shut off in the above operating conditions, the pilot valve 13 is on the Switching solenoid 78 is switched to its switching position in which the control channel 46 is shut off and the pilot control line 70 is connected to the pilot pressure channel 72. The control piston of the pressure compensator 42 is moved by the pump pressure in its closed position - the refilling of the increasing cylinder side does not take place and the "saved" pressure medium volume flow can be used to supply other consumers.

Disclosed are a valve arrangement and a method for controlling a double-acting consumer, in particular a lifting mechanism of a mobile working device, wherein a consumer an adjustable metering orifice and an individual pressure compensator is assigned, via which the pressure difference across the metering orifice can be kept constant constant load pressure. According to the invention, the individual pressure compensator can be in predetermined operating states Switch from the load pressure in a blocking position, so that the pressure medium supply is shut off to the consumer, although the metering orifice is opened further.

LIST OF REFERENCE NUMBERS

2

Rear linkage

4

lifting gear

6

lifting cylinder

8th

variable

10

inlet channel

12

pressure compensator

13

pilot valve

14

way valve

16

tank channel

18

working channel

20

working channel

22

lowering module

24

lowering module

26

Pressure relief valve

28

Secondary pressure relief valve

30

annulus

32

pressure chamber

34

Hubwelle

36

poor

38

attachment

40

Compensator spring

42

channel

44

LS-channel

45

pilot element

46

control channel

47

pilot element

49

Control oil supply

50

valve slide

52

control line

54

control line

56

Return spring arrangement

58

feather

60

Pressure balance channel

62

Pressure balance channel

64

Entsperrkanal

66

Entsperrkanal

70

Pilot control line

72

Pilot pressure channel

74

Pilot valve spring

76

jet

78

switching magnet

Claims (9)

1. Valve arrangement for controlling a double-acting consumer, especially a lifting unit (2) or a mounted implement of an agricultural utility vehicle, having a continuously adjustable directional control valve (14) which forms a metering restrictor and with which is associated an individual pressure regulator (12) for keeping constant the pressure difference above the metering restrictor and by means of which a pressure chamber (30, 32) of the consumer can be connected to a pressure medium source and another pressure chamber (32, 30) can be connected to a pressure medium sink, characterised in that the individual pressure regulator (12) can be switched over into a blocking position irrespective of the load pressure.
2. Valve arrangement according to patent claim 1, having a pilot valve (13) by means of which a control face of a control piston of the individual pressure regulator (12), which control face acts in the closing direction, can be acted upon by the pressure of the pressure medium source in order to bring the control piston into its blocking position.
3. Valve arrangement according to patent claim 2, wherein the pilot valve (13) is an electrically actuated 2-way switching valve which, in its spring-biased basic position, blocks off a connection between a control chamber, delimited by the control face of the control piston, and a feed duct (10) conducting the pump pressure and, in its switching position, opens that connection.
4. Valve arrangement according to patent claim 2 or 3, wherein the control chamber is connected by way of a control duct (46) to a portion of the pressure medium flow path leading to the consumer (6), and a nozzle (76) is arranged in the control duct (46).
5. Valve arrangement according to patent claim 2, wherein the pilot valve (13) is a 3/2-way switching valve which, in its spring-biased basic position, blocks off a connection between the control chamber, delimited by the control face, and a feed duct (10) conducting the pump pressure and opens the connection between the control chamber and a portion of the pressure medium flow path to the consumer (6) and, in its switching position, blocks off that connection and acts on the control chamber with the pressure in the feed duct (10).
6. Valve arrangement according to any one of the preceding patent claims, wherein the individual pressure regulator (12) is a load-sensing pressure compensator connected upstream or downstream of the metering restrictor or is a load-independent flow distribution pressure compensator.
7. Valve arrangement according to any one of the claims related to patent claim 3 or 5, wherein the switching-over of the pilot valve (13) takes place with the on-board voltage in dependence on specific operating conditions.
8. Method for controlling a double-acting consumer, especially a lifting unit of a mobile working device, a pressure chamber (30) of the consumer being supplied with pressure medium by means of a metering restrictor and an individual pressure regulator (12), and another pressure chamber (32) being connected to a pressure medium sink, characterised in that the individual pressure regulator (12), in dependence on various operating conditions, is switched into its blocking position, irrespective of the load pressure at the consumer, in order to block the flow of pressure medium to the pressure chamber (30).
9. Method according to patent claim 8, wherein the switching-over takes place when a replenishing of an expanding pressure chamber (30) of the consumer (6) is unnecessary.

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